The technical field of the invention is that of a consumer electronics device based on wireless transmission of information. The range of transmissions is purely local (i.e., short distances up to thirty meters, more or less) and designed to provide a personal transmission channel from a nearby audio source such as a tape recorder, record player, compact-disk player, radio set, and so forth. The transmitter and receiver technology operate in the standard radio-frequency bands such as the US 88 Megahertz (MHz) to 108 MHz FM band or in the unregulated low-power bands where standard frequency- and phase-modulation techniques are employed or in the very-low frequency band where pulse-modulation techniques are common.
The field of consumer audio electronics comprises a wide variety of personal listening devicesxe2x80x94from hand-held and wearable radios and communicators to portable devices for retrieving audio information stored in many forms such as cassette-tape media and compact-disk media of various types. There also exist various earphone devices auxiliary to or integral with many of these personal entertainment devices. The vast majority of these personal listening or entertainment devices require that the sound storage and playback unit, i.e., the sound source that produces an electrical signal in the audio range, be carried along with the user. A majority of these later devices that are equipped with personal earphone units send an electrical signal from the playback device to the earphone device via a cable or wire, potentially encumbering the user or providing an easily noticed indicator that the user is engaged in some sort of entertainment activity via an audio source. Of course, there are a large number of such commercial devices, ranging from those trade-marked to those fully patent-protected, that are easily recognizable in the marketplace. It is to be noted that the field of such devices, comprising the bulk of the prior art, is too large to enumerate in this document. The following discussion will be restricted to devices that are more clearly and particularly focused in the field of the present invention.
A commonly encountered device is a fully functional FM or AM radio built into a set of wearable headphones. The advantages are complete portability, wearability, and tuneability over the full broadcast bands, including stereo reception for the FM band. For example U.S. Pat. No. 4,930,148 describes a headband radiophone containing a receiver-transmitter to reciprocally transmit or receive signals. Another example is furnished by U.S. Pat. No. 5,095,382 which describes a wireless headphone designed to reciprocally transmit and receive signals by means of an infrared beam of light.
There are also several types of wireless headphones on the market primarily designed to allow the user to listen to audio sources such as television or a home-music or entertainment center without disturbing others. The wireless nature of said devices allows the user freedom to move about within the restricted range of the transmissions without being encumbered by wires or cables precisely as in the present invention. These wireless headsets are meant for use in restricted areas usually confined to a few rooms in or near a dwelling and do not provide capacity for a plurality of channels for multiple users. The latter capability is achieved by purchasing multiple units. As each device comes with its own pre-assigned channel, these devices are not suitable for group activities. The present invention would fulfill the stated purposes of these existing devices yet not be burdened with the aforementioned restrictions and limitations. In particular, the present invention allows multiple independent users in the same proximity by means of its self-programming function, and it allows multiple users to share in the same locally broadcast material without requiring multiple base units or transmitters.
Closer to the present invention is U.S. Pat. No. 5,677,964, which describes a transmitter-receiver system wherein the transmitter unit is installed in an audio equipment and the receiver unit is installed in an earphone. A goal here is to allow the user to listen to information transmitted from the audio equipment without interfering with others in the vicinity or having exposed wires or cables between the audio equipment and the listener.
An invention likewise close to the present invention in the area of miniaturization by describing a device fitting within the outer canal of the ear, is U.S. Pat. No. 5,734,976 which describes a micro-receiver for receiving a high-frequency frequency- or phase-modulated signal and is based on single integrated circuits in BiCMOS technology integrating the necessary amplifiers, oscillators, modulators, demodulators, filters and audio amplifier.
The description of U.S. Pat. No. 5,677,964 includes a transmitter partially fulfilling the role of the xe2x80x9cbase unitxe2x80x9d described in the present invention. That of U.S. Pat. No. 5,734,976 is primarily concerned with a prosthetic hearing-aid device, yet certainly meets one of the desired goals of the present invention in being small, lightweight, unobtrusive, and capable of being worn in the outer canal of the ear and containing the required receiver circuitry and power supply. Neither of these descriptions considers a base unit that automatically selects the first available frequency band for transmissions, or a base unit that automatically programs the receiver unit to receive transmissions on said frequency band, or a base unit that is functionally as portable as the receiver unit. The second description also implies that the associated transmitter unit is to be worn by the user as necessitated by utility of prosthetic hearing-aid devices. Combining the essential ideas present in these two existing inventions approaches, but does not reach, the functionality and convenience of the proposed invention.
The idea of the invention is to provide a private and unobtrusive means for a user to listen to a local (nearby) source of music or other audio entertainment or information on a dynamically selected channel that is simple to establish and does not interfere with possibly many other users at the same location. Logically and physically, the invention comprises two distinct modules: (1) a receiver or earphone and (2) a transmitter or base unit. It is thus the intention of the invention to provide a wireless connection between the earphones and base unit, allowing the user to move freely about, unencumbered by cables or wires, within the limited range of the base unit""s transmissions. It is a primary intention of this invention to allow multiple users in the same location either to listen to independent sources of entertainment or information or, if desired, to share such sources with others possessing similar receiver units (earphones). Further, it is the intention of the invention that the receiver unit be small, compact, lightweight, and unobtrusive both visually and kinesthetically.
The first module consists of a lightweight, wireless, radio-frequency receiver or receiver pair (for stereo sources) mounted in lightweight headphone or head set or earphones. xe2x80x9cEarphonesxe2x80x9d in the following description is understood to refer to any convenient ear-external or internal device consistent with the contained receiver units. The earphones may be either externally worn or internally fitted to be placed in the outer canal of the ear, as the user desires. Furthermore, the earphone receiver units are xe2x80x9cself-programedxe2x80x9d as described below. This latter feature ensures simplicity of operation and ease of use while maintaining flexibility of multiple devices operating in the same local area while minimizing inter-unit interference.
The second module, the transmitter or base unit, has four functions: (1) to select automatically a clear transmission channel for said transmission, (2) to program or lock the earphones to receive exclusively on said automatically preselected channel, (3) to modulate an appropriate radio frequency on said channel by the chosen audio-level input for low-power transmission to the earphones, and (4) to provide power to the earphones by way of charging their contained batteries. The base unit is likewise small, lightweight, and portable, being just large enough to contain (1) the scanning circuitry, (2) the programming circuitry, (3) the transmitter circuitry, (4) the battery-charging circuitry, (5) minimal controls and indicators, (6) appropriate signal connectors, and (7) a battery or other type of power supply.
In a typical situation, the user switches both the earphones and the base unit to the xe2x80x9conxe2x80x9d position as indicated by small light-emitting diode indicators and then inserts the earphones into specially designed receptacles located in the base unit. The power-on action initiates charging of the earphone batteries should they require it. This power-on action also initiates a xe2x80x9cscanxe2x80x9d function comprising a sequence of events that (1) effectively searches for an xe2x80x9copenxe2x80x9d channel, (2) locks a frequency synthesizer or phase-locked loop to the frequency of the first open channel thus located, and (3) sends a xe2x80x9clockxe2x80x9d command via contacts located in the receptacles to a frequency synthesizer or phase-locked loop in each of the earphones. At the end of this xe2x80x9cauto-programingxe2x80x9d sequence, (4) a xe2x80x9creadyxe2x80x9d indicator or signal indicates that the user may now remove the earphones and place them in position for listening, moving about the area as desired, within the limited range of the base-unit""s transmitter, receiving the audio information from the source connected to the base unit via the standard process of demodulation, amplification, and presentation of the electrical signal thus obtained to the earphones"" electrical-acoustic transducers.
Other users of similar devices located within the same transmission range, or even in overlapping transmission areas of the first device, will not find an open channel at the same frequency chosen by the unit just programmed or any active prior-activated units as well. Any base unit attempting to program its own earphones will scan for the first clear channel starting at one end of the selected spectrum, ensuring that no user will interfere with any other and no strong, established broadcasts will interfere with a user""s auto-selected channel. The number of channels available in any area depends on the broadcast band chosen and the bandwidth (plus guard band) for each device. As an example, assume parameters consistent with the standard US FM broadcast band of 88 to 108 MHz and 100 KHz bands, there would be xe2x80x9croomxe2x80x9d for perhaps 200 independent users, not accounting for any strong commercial FM broadcasts, which would reduce this number by at least one unit for each such strong station.
If other users of an identical device within the same transmission range wished to listen on a common channel and hence to the same audio source as provided via transmission by any given base unit, they would simply place their compatible earphones into the receptacles of said base unit and depress a secondary xe2x80x9cprogramxe2x80x9d or xe2x80x9clockxe2x80x9d control button. Such action would lock their earphones to the preselected channel of the chosen unit. In this manner, multiple users can listen to the same source, allowing for class or shared-listening activity.
Due to its compact nature, the earphone electronics are fabricated with surface-mount methods using standard integrated circuits and monolithic lumped components. Discrete components are used in the circuit where necessary to establish externally selected frequency ranges as well as other functions such as passive filters. Both receiver and transmitter units are separately powered, with the receiver earphones having a battery power supply, and the base unit either a battery or other means of power.
The key features of the invention are summarized as its ability to avoid interference with commercial broadcasts due to the auto-scan feature; to be compliant with communication authorities"" rules of low power and short range in certain restricted bands; to its xe2x80x9cfoolproofxe2x80x9d use based on minimal controls and no adjustments; to provide wireless operation; to contain rechargeable or replaceable batteries in base unit; to contain rechargeable and/or replaceable batteries in earphones; to restrict the physical dimensions of the base unit into a small, compact, lightweight, and easily transportable and detachable module independent from any particular source of program material; and to provide the user with the earphones that are ultra-light weight and/or fit in outer ear or mounted on a lightweight, supporting frame.
Although the primary conception and purpose of this invention is to provide an auxiliary but extended capability for standard sources of audio material in the sense that any source device having the required xe2x80x9csignalxe2x80x9d or xe2x80x9caudioxe2x80x9d output connector with compatible impedance characteristics can be connected to the base unit described in this invention, there are numerous variations possible based on the described invention besides the mentioned uses of transmitting local audio sources to listeners not wishing to be encumbered by wires or highly visible head pieces. These variations may be differentiated, among other characteristics, by various sources for the transmitted audio material. The preferred embodiment presented herein should in no way restrict the present invention to a particular configuration as regards usage.
A modification of the base unit could be made with a built-in microphone or an input with an impedance-matching amplifier and gain control designed for such a microphone. Such a unit could be used to send verbal messages or any other sound based on sound pressure waves to those with compatible earphones. For example, a type of selective-broadcast communication only to users having completed the xe2x80x9clockxe2x80x9d process with the centrally chosen base unit could be established, allowing only those users to receive said communication, even though in a crowd or noisy location.
A modification of the base unit could be made to equip it with a built-in radio receiver allowing the user to select a local radio station for listening remotely from said radio receiver. Otherwise and more generally stated, the standard types of sound reproduction devices could incorporate the invention described here rather than said invention serving said devices as an auxiliary. In which case, the auto-scanning and self-programming functions would be retained as essential to benefit from the innovations described herein.